Do not set a wallclock time limit if there is no time limit.

src/tools/cpulimit.c

@@ -82,15 +82,17 @@ int main(int argc, char *argv[]) {
     if (pid > 0) {
       int status;
       pid_t p;
-      struct sigaction sa;
 
+      if (timelimit) {
         /* set a wallclock time limit as last resort */
+        struct sigaction sa;
         sa.sa_handler = &wallclock_timelimit_reached;
         sigemptyset(&sa.sa_mask);
         sa.sa_flags = 0;
         sigaction(SIGALRM, &sa, NULL);
         wallclock_timelimit = 2*timelimit + 60;
         alarm(wallclock_timelimit);
+      }
 
       /* wait for the subprocess */
       p = waitpid(pid, &status, 0);